# white-dwarf merge in binaries

Two white dwarfs with a total mass $>1.4\:M_{\odot}$ merge. It may trigger a type Ia SN explosion.

How about the three cases below?

1. Two low mass WDs merge, total mass $<1.4\:M_{\odot}$.

2. A low mass WD + a low mass neutron star, total mass $<2\:M_{\odot}$ but $>1.4\:M_{\odot}$.

3. A low mass WD + a neutron star, total mass $>2\:M_{\odot}$.

If any of the above can result in a SN, have we observed this kind of SN?

• Are you talking direct hit collisions or the more gradual, tight orbit, gradual collisions as they spin around each other thousands of times. The 2nd type of collision is far more common. – userLTK Nov 6 '16 at 17:35
• @ltk I have revised the title. A 0.5 wd+ 1.4ns should be common. – questionhang Nov 7 '16 at 4:26
• @questionhang I guess you're referring to the latter? – Sir Cumference Nov 7 '16 at 13:19
• @sir yes, in binaries. – questionhang Nov 7 '16 at 14:00